不同树龄香榧土壤有机碳特征及其与土壤养分的关系

该研究以浙江省诸暨市的香榧国家森林公园5个树龄段(0~50、50~100、100~300、300~500和500a以上)的香榧(Torreyagrandis)为研究对象,通过野外采集土壤样品,分析其0~20、20~40、40~60cm土层土壤总有机碳(TOC)、易氧化碳(ROC)、轻组有机质(LFOM)及土壤养分含量,探讨不同树龄香榧土壤有机碳变化规律,为香榧林的土壤质量评价与持续利用,以及香榧古树的保护提供理论依据。结果表明:(1)不同树龄香榧土壤的总有机碳、易氧化碳和轻组有机质含量均随香榧树龄的增加呈先增大后减小的趋势,且300~500a生的数值最大,但易氧化碳与轻组有机质含量在各树龄间的差异不明显。(2)不同树龄香榧土壤中易氧化碳占总有机碳的比例总体表现为:50~100a0~50a100~300a300~500a500a以上(0~20cm土层除外)。(3)各树龄段香榧土壤易氧化碳和轻组有机质含量与土壤总有机碳之间的相关性均达到极显著水平;不同树龄段香榧土壤总有机碳、各活性有机碳组分与全氮(TN)、水解性氮(AN)、有效磷(AP)之间的相关性较好(0~50a生除外),与速效钾(AK)、交换性钙(Ca)和交换性镁(Mg)之间的相关性较差(500a以上除外);500a以上香榧土壤总有机碳、各活性有机碳组分与土壤养分的相关性均达到极显著水平。

Relationships between Soil Organic Carbon Characteristics and Soil Nutrients for Different Tree age Torreya grandis

In the Torreya grandis National Forest Park in Zhuji, Zhejiang, Torreya grandis with five age groups (0-50, 50-100, 100-300, 300-500 and over 500 years) were selected for this study. Soil samples were collected in the field to analyze the total soil organic carbon (TOC), readily oxidizable carbon (ROC), light fraction organic matter (LFOM), and soil nutrient contents in 0-20, 20-40, and 40-60 cm soil layers. The changes of soil organic carbon for different tree age T. grandis were studied in this paper, which provided theoretical basis for the evaluation and sustainable use of the soil quality in forest stands, and the conservation of the old T. grandis. The results showed that, (1) the TOC, ROC and LFOM increased firstly and then decreased with the increase of the tree age, among which the content was the highest for the 300-500 years group. However, significant differences among tree ages were not found in the ROC and LFOM. (2) The ratio of ROC to TOC for different tree age T. grandis was: 50-100>0-50>100-300>300-500>500 years (except 0-20 cm soil layer). (3) The correlations between ROC, LFOM, and TOC in all age groups are extremely significant. The correlations between TOC, various active organic carbon component, total nitrogen, available nitrogen and available phosphorus were relatively strong at different ages (except for 0-50 years). The correlation between TOC, various active organic carbon component, available kalium, exchangeable calcium, and exchangeable magnesium were relatively weak (except for over 500 years). The correlations of TOC, active organic carbon component, and soil nutrients over 500 years were extremely significant.